Cloning plants

Diligent research and biotechnology have again scored another amazing feat. Researchers at USDA's Agricultural Research Service (ARS) in Wood-ward, OK, along with Russian scientists, have patented a hybrid between corn and its distant relative, eastern gamagrass, which can naturally clone itself. The development of the hybrid should eventually lead to hybrid corn lines that reproduce themselves without loss in hybrid vigor, disease resistance or favorable agronomic attributes.

A milestone. The ARS patent marks a milestone for plant geneticists. For the plant to clone itself, the genes controlling the trait had to be transferred from gamagrass to corn. Though far from being useful at a commercial level, this accomplishment shows that a sexually reproducing plant can be changed into an asexual variety.

The new asexual plant reproduces when its embryos grow from egg cells without being fertilized by pollen. This form of asexual reproduction is apomixis.

Apomixis occurs naturally in some plants. Scientists have identified more than 300 species that reproduce by cloning themselves through their seeds. Many successful lawn grasses like Kentucky bluegrass as well as common weeds like dandelions reproduce their seed this way.

Major plant laboratories around the world have worked to move apomixis into field crop varieties such as rice, wheat, corn and sorghum. However, the USDA-ARS research laboratory was the first to successfully use this technology in an important cereal grain.

The Southern Plains Research Station in Oklahoma and the Institute of Genetics in Siberia, Russia, are joint inventors on the apomictic maize patent.

"This is not a miracle that will change everything in plant breeding," reports Phillip Sims, ARS researcher. "It's another advancement that the seed industry needs to reflect on when they go about their work. It doesn't eliminate the development of new and improved plants.

"Besides, we've got a long way to go with this work, including isolation of the gene," he adds.

Sims and the other researchers are now trying to pinpoint the actual apomictic gene or genes in a sample of apomictic corn-eastern gamagrass hybrids. Once the genes are pinpointed, they could be transferred to other corn lines or cereal crops.

"The new apomictic corn is still a long way from a midwestern farmer's planter," Sims says. "It could be 5 to 10 years before farmers see this trait in seed they purchase."

Grass genes. The ARS scientists credit the pioneering work of Russian geneticist Dimitri Petrov for laying the groundwork for their apomictic work. Petrov's work in hybridizing corn and eastern gamagrass began in the 1960s. In 1993, the Russian institute entered a four-year cooperative agreement with USDA-ARS for continuing apomictic research. The Russian research was reevaluated and new apomictic materials were developed. Eventually, the research resulted in the generation of plants that are very similar to corn. The development of these plants led to the application for the patent.

The work on corn and eastern gamagrass may yield a better forage plant. Gamagrass is a perennial warm-season grass that is relished by grazing livestock. "The work on gamagrass gives us an opportunity to build a better perennial grass for farmers and ranchers to use in the central United States, " Sims says. "It just happens to have a common ancestor to corn."

Widespread use. ARS reports that several seed companies are interested in its patent. Companies will be able to enter licensing agreements with ARS for use of the genes in hybrid corn. Sims says that the agency wants to make this technology widely available.

"The government is not in the corn business," adds ARS researcher Chester Deald. "Our main goal is to see this is used to the benefit of mankind."